1. Field of the Invention
The present invention relates to an image forming apparatus for reproducing an image from image data supplied from an image output apparatus, and more particularly to an image forming apparatus for reproducing an image by superimposing thereon an identification pattern for identifying the image output apparatus that supplied the image data.
2. Description of the Related Art
In recent years, digital color image forming apparatuses (copying machines, printers, etc.) capable of faithfully reproducing color images have been introduced commercially, and recording media (recording paper, etc.) with color images reproduced thereon can be easily obtained. Some image forming apparatuses are designed not only as digital color copying machines to make copies of document images, but also as printers to form images based on image data supplied from external apparatuses. Using such a digital color copying machine equipped with a function as a so-called network printer, a recording medium with a color image formed thereon can be easily prepared from image data supplied from any one of a plurality of image output apparatuses connected to the network.
As faithfully reproduced color images can be easily obtained using such image forming apparatuses, there arises the concern that image forming apparatuses might be used for wrongful purposes, for example, for illegal replication of images, such as bank notes and securities, replication of which is prohibited.
To address this situation, Japanese Examined Patent Publication JP-B2 2614369 discloses a configuration wherein when recording an inputted color image on a recording medium for reproduction, a pattern image representing identification information unique to the image forming apparatus is added using a color material that is difficult to discern by the human eye. On the other hand, Japanese Unexamined Patent Publication JP-A 61-285578 (1986) discloses an electronic file system wherein when viewing image information stored in an electronic file apparatus, code information for identifying the user is entered and, when outputting retrieved image information, a pattern image identifying the user is superimposed on the retrieved image for output. Further, Japanese Unexamined Patent Publication JP-A 6-326854 (1994) discloses a configuration wherein an image is outputted appending thereto image information which indicates which image output source outputted the image among a plurality of image output sources, i.e., external apparatuses connected to the image forming apparatus.
However, any of the above prior art configurations can only be applied in an environment where users or apparatuses that are allowed to use the image forming apparatus are predetermined, and cannot be applied in an environment where unspecified individuals or apparatuses are expected to use the image forming apparatus; therefore, the prior art has had the problem that illegal conducts such as the forgery of bank notes, securities, etc. cannot be prevented securely.
In recent years, a variety of portable peripheral apparatuses such as digital cameras and portable terminal apparatuses that handle images as data have been commercialized, and various methods have been standardized as data communication methods for connecting such peripheral apparatuses to image forming apparatuses. It has also been proposed to input color image data, created by portable image output apparatuses such as digital cameras and portable terminal apparatuses, into image forming apparatuses via interfaces such as IrDA without using any cables. If image forming apparatuses equipped with such interfaces are installed in stores such as convenience stores, situations are expected to occur that make it quite easy for unspecified individuals to obtain faithfully reproduced color images using such image forming apparatuses. Any of the prior art apparatuses, however, cannot securely prevent illegal conducts because, with the prior art, the individual that is responsible for the illegal conduct or the image output apparatus that outputted the image constituting the illegal conduct cannot be identified from among unspecified individuals or apparatuses.
This problem is not limited to cases where image data are inputted from portable image output apparatuses without using cables, but can also occur in the case of image forming systems in which image data is inputted from an arbitrary image output apparatus, whether it is a portable type or a fixed type, to an image forming apparatus via a general-purpose cable or via a network open to the outside.